The present invention relates generally to methods and apparatuses for operating percutaneous probes, such as percutaneous electrodes used for electrical nerve stimulation.
Electrical therapy has long been used in medicine to treat pain and other conditions. For example, transcutaneous electrical nerve stimulation (TENS) systems deliver electrical energy through electrode patches placed on the surface of a patient""s skin to treat pain in tissue beneath and around the location of the patches. One problem with TENS systems is that they may not provide patients with adequate pain relief.
More recently, a technique in which electrodes are placed through the patient""s skin into the target tissue has been proposed. Percutaneous Neuromodulation Therapy is (xe2x80x9cPNTxe2x80x9d) (also sometimes called Percutaneous Electrical Nerve Stimulation or xe2x80x9cPENSxe2x80x9d) using percutaneously placed electrodes achieves significantly better pain relief results than TENS treatments using skin surface electrodes. This therapy is described in Ghoname et al., xe2x80x9cPercutaneous Electrical Nerve Stimulation for Low Back Pain,xe2x80x9d JAMA 281:818-23 (1999); Ghoname et al., xe2x80x9cThe Effect of Stimulus Frequency on the Analgesic Response to Percutaneous Electrical Nerve Stimulation in Patients with Chronic Low Back Pain,xe2x80x9d Anesth. Analg. 88:841-6 (1999); Ahmed et al,. xe2x80x9cPercutaneous Electrical Nerve Stimulation (PENS): A Complementary Therapy for the Management of Pain Secondary to Bony Metastasis,xe2x80x9d Clinical Journal of Pain 14:320-3 (1998); and Ahmed et al., xe2x80x9cPercutaneous Electrical Nerve Stimulation: An Alternative to Antiviral Drugs for Herpes Zoster,xe2x80x9d Anesth. Analg. 87:911-4 (1998). The contents of these references are incorporated herein by reference.
One method for applying percutaneous nerve stimulation is to insert acupuncture needles into the patient""s skin and attach the needles to waveform generators via cables and alligator clips to deliver a percutaneous electrical current. One drawback with this method is that the electrical connections to the needle may not be sufficiently secure and reliable. Another drawback with this method is that it may be difficult to accurately position the needles. For example, if a needle is placed too close to a nerve within a nerve region it is intended to treat, the needle itself may be painful and/or the amount of electrical current necessary to provide effective therapy may be painful. Accordingly, the practitioner may need to reposition the needle to a new location. However, it may be difficult for the practitioner to accurately reposition the needle. For example, the practitioner may lose track of the needle""s original position once the needle is removed. Without having the original position of the needle as a reference, the practitioner may be unable to accurately locate the new position. Furthermore, the practitioner may not be able to accurately control the angle at which the needle re-enters the skin at the new position. If the angle is different than the initial angle at which the needle entered the skin, the tip of the needle can end up at the same point it was before the repositioning process began.
The present invention is directed to methods and apparatuses for coupling a percutaneous electrode to a source of electrical power. A method in accordance with one aspect of the invention includes releasably engaging a first surface of a conductive member with the electrode, biasing the conductive member against the electrode, and moving the conductive member relative to the electrode at least until a contact feature having a second surface offset from the first surface engages the electrode. The method can further include receiving mechanical feedback when the contact feature engages the electrode, inserting the electrode into a patient""s skin, and coupling the conductive member to a source of electrical power.
In a further aspect of the invention, the method can include releasably coupling the conductive member to an actuator and rotating the actuator and the conductive member as a unit to engage the contact feature with the electrode. The contact feature have a circular cross-sectional shape and can include a dimple having a first portion facing opposite a second portion so that rotating the conductive member can include initially engaging the first portion of the dimple with the electrode and then engaging the second portion of the dimple with the electrode.
The invention is also directed toward an apparatus for administering percutaneous electrode stimulation and a method for forming such an apparatus. In one aspect of the invention, the apparatus can include a housing and an electrode movably coupled to the housing and having a sharpened end to pierce a skin surface. In another aspect of the invention, the apparatus can include an actuator releasably coupled to the electrode to move the electrode relative to the housing. The actuator can be movable relative to the electrode between a first position and a second position, and can have a conductive member coupleable to a source of electrical power. The conductive member can have a first surface and a conductive feature with a second surface offset from the first surface so that the conductive feature is releasably engaged with the electrode when the actuator is moved from the first position to the second position.